The present invention relates to applying decoration on an article, using a method of deposition by sublimation in which a sublimable ink carried by a flexible backing is transferred onto a face of the article by means of heat and pressure.
European patents EP-B1-0 451 067 and EP-B1-0 606 189 describe methods of this type.
The temperature at which the flexible backing needs to be raised in order to cause the ink to sublime lies typically in the range 140xc2x0 C. to 250xc2x0 C.
Thus, this method is used at present only for decorating articles made out of materials that can withstand such temperatures in satisfactory manner.
Nevertheless, in the field of packaging, it is common practice to make articles such as closure devices or receptacles out of polyethylene terephthalate or polypropylene.
Such articles cannot be decorated by known sublimation deposition methods since the heating of the flexible backing required for subliming the ink would give rise to deformation preventing such articles from being functional.
The present invention provides a novel method of deposition by sublimation enabling decoration to be applied onto an article, the method comprising the steps consisting in:
placing backing coated in a sublimable ink in contact with a face of the article; and
heating the backing with the help of heating means to cause the ink to sublime and be transferred onto the article, while cooling the opposite face of the article with the help of cooling means.
The invention makes it possible to decorate articles themselves made out of plastics materials whose ability to withstand high temperatures is normally insufficient to be capable of being decorated by known methods of deposition by sublimation.
Articles made of polyethylene terephthalate or of polypropylene can be decorated in this way.
It is also possible to decorate articles made of styrene-based thermoplastics (in particular polystyrenes including high impact polystyrene and super high impact polystyrene, and copolymers thereof, in particular SAN, ABS, MABS, NAS, ABS/PC, or polyacrylics).
By means of the new method of the invention, it is also possible to decorate a hollow article by applying the backing on an inside face of the article even if the article is of small dimensions since the corresponding outside face of the article is then cooled.
When the article is made of a transparent plastics material, it is possible to obtain particularly advantageous appearance effects when the decoration is deposited on the inside face thereof.
The above-mentioned heating means can comprise a flexible bag into which a hot, liquid or gaseous fluid is injected or blown, and preferably compressed hot air.
The flexible bag is easily inserted inside the article in the deflated state, and once inflated it serves to press the backing against the inside face of the article and to supply the heat necessary for causing the ink to sublime and be transferred.
The outside surface of such a heating member advantageously presents a certain amount of deformability, so as to fit closely to the shape of the inside face of the article.
The cooling means can be constituted by a cooling core on which the article is engaged when the decoration is applied to the outside face of the article.
When the decoration is applied to the inside face of the article, the cooling means can comprise means for blowing or spraying a stream of liquid or gaseous cooling fluid onto the outside face of the article, and preferably a stream of cold air.
The invention also provides an article decorated by means of a method as defined above.
The invention also provides a hollow article having decoration on its inside face that is obtained by subliming ink by means of a method comprising the steps consisting in:
placing backing coated in a sublimable ink in contact with an inside face of the article; and
heating the backing with the help of heating means to cause the ink to sublime and be transferred onto the article, while cooling the opposite face of the article as much as necessary with the help of cooling means.